Trainee journalist at Cardiff JOMEC, English & German graduate from the University of Exeter, former editor of Exeposé student newspaper and winner of 'Best Interview' at the 2017 Student Publication Association national awards.

The spy software is often disguised using names like “Browser” or “Facebook,” according to Ronald Eikenberg, IT security expert and editor of computing magazine c’t.

“You can hide one programme inside another,” he said.

When Facebook friends invite us to download games, we don’t always think about the potential risk, Eikenberg warned – but “the other programme can be running in the background, without us having any knowledge of its existence.”

Those worrying that they might have spyware installed can use an anti-virus programme to scan their smartphone, Eikenberg recommends.

App providers often try to protect themselves from legal issues by asking users to agree only to install the software on their own devices, or with the explicit permission of the device’s owner.

But terms and conditions such as these are no loophole, a spokesperson for Baden-Württemberg Ministry of Justice told DPA.